<PAGE>

                                                                   EXHIBIT 4.4-B


                            DUKE CAPITAL CORPORATION

                                       TO

                            THE CHASE MANHATTAN BANK

                                                    Trustee

                               ----------------

                                Supplemental Indenture

                          Dated as of          ,

                               ----------------

                                  $

                     Series     % Junior Subordinated Notes

                              due          ,

                               ----------------
<PAGE>

                             TABLE OF CONTENTS (1)

                                   ARTICLE 1

                     Series     % Junior Subordinated Notes

<TABLE>
<CAPTION>
                                                                           Page
                                                                           ----
 <C>          <S>                                                          <C>
 Section 101. Establishment.............................................     1
 Section 102. Definitions...............................................     2
 Section 103. Payment of Principal and Interest.........................     4
 Section 104. Deferral of Interest Payments.............................     5
 Section 105. Denominations.............................................     6
 Section 106. Global Securities.........................................     6
 Section 107. Redemption................................................     7
 Section 108. Additional Interest.......................................     7
 Section 109. Limitations on Dividend and Certain Other Payments........     8
 Section 110. Covenants Regarding Securities Trust......................     8
 Section 111. No Fiduciary Duty of Trustee to Holders of Trust
               Securities...............................................     9
 Section 112. Listing of Series   Notes.................................     9
 Section 113. Covenant Defeasance.......................................     9
 Section 114. Set-Off...................................................     9
 Section 115. Subordination.............................................     9
 Section 116. Paying Agent..............................................     9

                                   ARTICLE 2

                            Miscellaneous Provisions

 Section 201. Recitals by Corporation...................................     9
 Section 202. Ratification and Incorporation of Original Indenture......    10
 Section 203. Executed in Counterparts..................................    10
 Section 204. Assignment................................................    10
 Section 205. Enforcement by Holders of Preferred Securities of Right of
              Holders to Receive Principal and Interest.................    10
</TABLE>
--------
(1) This Table of Contents does not constitute part of the Indenture or have
    any bearing upon the interpretation of any of its terms and provisions.

                                       i
<PAGE>

THIS      SUPPLEMENTAL INDENTURE is made as of the      day of       ,     , by
and between DUKE CAPITAL CORPORATION, a Delaware corporation, having its
principal office at 526 South Church Street, Charlotte, North Carolina 28202
(the "Corporation"), and THE CHASE MANHATTAN BANK, a New York banking
corporation, as Trustee (herein called the "Trustee").

                              W I T N E S S E T H:

WHEREAS, the Corporation has heretofore entered into a Subordinated Indenture,
dated as of April 1, 1998 (the "Original Indenture") with The Chase Manhattan
Bank, as Trustee;

WHEREAS, the Original Indenture is incorporated herein by this reference and
the Original Indenture, as amended and supplemented to the date hereof,
including by this     Supplemental Indenture, is herein called the "Indenture";

WHEREAS, under the Indenture, a new series of Securities may at any time be
established in accordance with the provisions of the Indenture and the terms of
such series may be described by a supplemental indenture executed by the
Corporation and the Trustee;

WHEREAS, the Corporation proposes to create under the Indenture a new series of
Securities;

WHEREAS, additional Securities of other series hereafter established, except as
may be limited in the Indenture as at the time supplemented and modified, may
be issued from time to time pursuant to the Indenture as at the time
supplemented and modified; and

WHEREAS, all conditions necessary to authorize the execution and delivery of
this     Supplemental Indenture and to make it a valid and binding obligation
of the Corporation have been done or performed.

NOW, THEREFORE, in consideration of the agreements and obligations set forth
herein and for other good and valuable consideration, the sufficiency of which
is hereby acknowledged, the parties hereto hereby agree as follows:

                                   ARTICLE 1

                     Series     % Junior Subordinated Notes

Section 101. Establishment. There is hereby established a new series of
Securities to be issued under the Indenture, to be designated as the
Corporation's Series     % Junior Subordinated Notes due           ,      (the
"Series   Notes").

There are to be authenticated and delivered $            principal amount of
Series   Notes, and no further Series   Notes shall be authenticated and
delivered except as provided by Sections 304, 305, 306, 906 or 1106 of the
Original Indenture. The Series   Notes shall be issued in definitive fully
registered form without coupons.


                                       1
<PAGE>

The Series   Notes shall be in substantially the form set out in Exhibit A
hereto. The entire principal amount of the Series   Notes shall initially be
evidenced by one certificate issued to the Property Trustee of Duke Capital
Financing Trust [ ].

The form of the Trustee's Certificate of Authentication for the Series   Notes
shall be in substantially the form set forth in Exhibit B hereto.

Each Series   Note shall be dated the date of authentication thereof and shall
bear interest from the date of original issuance thereof or from the most
recent Interest Payment Date to which interest has been paid or duly provided
for.

Section 102. Definitions. The following defined terms used herein shall, unless
the context otherwise requires, have the meanings specified below. Capitalized
terms used herein for which no definition is provided herein shall have the
meanings set forth in the Original Indenture.

"Additional Interest" means (i) such additional amounts as may be required so
that the net amounts received and retained by the Holder (if the Holder is the
Securities Trust) after paying taxes, duties, assessments or governmental
charges of whatever nature (other than withholding taxes) imposed by the United
States or any other taxing authority will not be less than the amounts the
Holder would have received had not such taxes, duties, assessments, or other
governmental charges been imposed; and (ii) such interest as shall accrue on
interest due and not paid on an Interest Payment Date, accruing at the rate of
  % per annum from the applicable Interest Payment Date to the date of payment,
compounded quarterly, on each Interest Payment Date, to the extent permitted by
applicable law.

"Business Day" means a day other than (i) a Saturday or a Sunday, (ii) a day on
which banks in New York, New York are authorized or obligated by law or
executive order to remain closed or (iii) a day on which the Corporate Trust
Office or the principal corporate trust office of the Property Trustee is
closed for business.

"Deferred Interest" means such installments of interest as are not paid during
any Extension Period, plus Additional Interest (as defined in clause (ii) of
the definition thereof) thereon.

"Extension Period" means any period during which the Corporation has agreed or
elected to defer payments of interest, which deferral may be for a period of up
to    ( ) consecutive quarters.

"Guarantee" means the Guarantee Agreement executed and delivered by the
Corporation and The Chase Manhattan Bank, as guarantee trustee, for the benefit
of the holders of the Preferred Securities, as such Agreement may be amended
from time to time.

"Interest Payment Dates" means March 31, June 30, September 30 and December 31
of each year.

"Investment Company Act Event" means that the Administrative Trustees (as
defined in the Trust Agreement) and the Corporation shall have received an
Opinion of Counsel experienced in such matters to the effect that, as a result
of the occurrence of a change in law or regulation or a written change in
interpretation or application of law or regulation by any legislative body,
court, governmental agency or regulatory authority, there is more than an
insubstantial risk that the

                                       2
<PAGE>

Securities Trust is or will be considered an "investment company" that is
required to be registered under the Investment Company Act of 1940, as amended,
which change becomes effective on or after the Original Issue Date.

"Original Issue Date" means          ,     .

"Outstanding," when used with respect to the Series   Notes, means, as of the
date of determination, all Series   Notes theretofore authenticated and
delivered under the Indenture, except:

  (i) Series   Notes theretofore canceled by the Trustee or delivered to the
  Trustee for cancellation;

  (ii) Series   Notes for whose payment or redemption the necessary amount of
  money or money's worth has been theretofore deposited with the Trustee or
  any Paying Agent (other than the Corporation) in trust or set aside and
  segregated in trust by the Corporation (if the Corporation shall act as its
  own Paying Agent) for the Holders of such Series   Notes; provided that if
  such Series   Notes are to be redeemed, notice of such redemption has been
  duly given pursuant to the Indenture or provision therefor satisfactory to
  the Trustee has been made;

  (iii) Series   Notes as to which Defeasance has been effected pursuant to
  Section 1302 of the Original Indenture; and

  (iv) Series   Notes that have been paid or in exchange for or in lieu of
  which other Series   Notes have been authenticated and delivered pursuant
  to the Indenture, other than any such Series   Notes in respect of which
  there shall have been presented to the Trustee proof satisfactory to it
  that such Series   Notes are held by a bona fide purchaser in whose hands
  such Series   Notes are valid obligations of the Corporation;

provided, however, that in determining, during any period in which any Series
Notes are owned by any Person other than the Corporation or any Affiliate
thereof, whether the Holders of the requisite principal amount of Outstanding
Series   Notes have given, made or taken any request, demand, authorization,
direction, notice, consent, waiver or other action hereunder as of any date,
Series   Notes owned, whether of record or beneficially, by the Corporation or
any Affiliate thereof (with the exception of the Securities Trust) shall be
disregarded and deemed not to be Outstanding. In determining whether the
Trustee shall be protected in relying upon such request, demand, authorization,
direction, notice, consent, waiver or other action, only Series   Notes that
the Trustee knows to be so owned by the Corporation or an Affiliate of the
Corporation (with the exception of the Securities Trust) in the above
circumstances shall be so disregarded. Series   Notes so owned that have been
pledged in good faith may be regarded as Outstanding if the pledgee establishes
to the satisfaction of the Trustee the pledgee's right so to act with respect
to such Series   Notes and that the pledgee is not the Corporation or any
Affiliate of the Corporation.

"Preferred Securities" means the   % Trust Preferred Securities issued by the
Securities Trust.

"Property Trustee," when used with respect to the Series   Notes, means the
Person designated as such in the Trust Agreement.

                                       3
<PAGE>

"Regular Record Date" means, with respect to each Interest Payment Date, the
close of business on the 15th calendar day preceding such Interest Payment
Date.

"Securities Trust" means Duke Capital Financing Trust   , a statutory business
trust formed by the Corporation under Delaware law to issue the Trust
Securities, the proceeds of which will be used to purchase Series   Notes, or a
successor thereof.

"Special Event" means an Investment Company Act Event or Tax Event.

"Stated Maturity" means          ,     .

"Tax Event" means that the Administrative Trustees and the Corporation shall
have received an Opinion of Counsel experienced in such matters to the effect
that, as a result of (a) any amendment to, or change (including any announced
prospective change) in, laws (or any regulations thereunder) of the United
States or any political subdivision or taxing authority thereof or therein or
(b) any amendment to, or change in, an interpretation or application of such
laws or regulations, there is more than an insubstantial risk that (i) the
Securities Trust would be subject to United States federal income tax with
respect to income accrued or received on the Series   Notes, (ii) interest
payable on the Series   Notes would not be deductible by the Corporation for
United States federal income tax purposes, or (iii) the Securities Trust would
be subject to more than a de minimis amount of other taxes, duties or other
governmental charges, which change or amendment becomes effective on or after
the Original Issue Date.

"Trust Agreement" means the Amended and Restated Trust Agreement that governs
the affairs of the Securities Trust.

"Trust Securities" means the securities issued by the Securities Trust
evidencing the entire beneficial interest therein.

Section 103. Payment of Principal and Interest. The unpaid principal amount of
the Series   Notes shall bear interest at the rate of   % per annum until paid
or duly provided for, such interest to accrue from           ,      or from the
most recent Interest Payment Date to which interest has been paid or duly
provided for. Interest shall be paid quarterly in arrears on each Interest
Payment Date commencing            ,      to the Person in whose name the
Series   Notes are registered on the Regular Record Date for such Interest
Payment Date; provided that interest payable at the Stated Maturity of
principal or on a Redemption Date as provided herein will be paid to the Person
to whom principal is payable. So long as an Extension Period is not occurring,
any such interest that is not so punctually paid or duly provided for will
forthwith cease to be payable to the Holders on such Regular Record Date and
may either be paid to the Person or Persons in whose name the Series   Notes
are registered at the close of business on a Special Record Date for the
payment of such defaulted interest to be fixed by the Trustee ("Special Record
Date"), notice whereof shall be given to Holders of the Series   Notes not less
than ten (10) days prior to such Special Record Date, or be paid at any time in
any other lawful manner not inconsistent with the requirements of any
securities exchange, if any, on which the Series   Notes may be listed, and
upon such notice as may be required by any such exchange, all as more fully
provided in the Original Indenture.


                                       4
<PAGE>

Payments of interest on the Series   Notes will include interest accrued to but
excluding the respective Interest Payment Dates. Interest payments for the
Series   Notes shall be computed and paid on the basis of a 360-day year of
twelve 30-day months. In the event that any date on which interest is payable
on the Series   Notes is not a Business Day, then payment of the interest
payable on such date will be made on the next succeeding day that is a Business
Day (and without any interest or payment in respect of any such delay), except
that, if such Business Day is in the next succeeding calendar year, such
payment shall be made on the immediately preceding Business Day, in each case
with the same force and effect as if made on the date the payment was
originally payable.

Payment of the principal and interest (including Additional Interest, if any)
on the Series   Notes shall be made at the office of the Paying Agent in such
coin or currency of the United States of America as at the time of payment is
legal tender for payment of public and private debts, with any such payment
that is due at the Stated Maturity or at earlier redemption of any Series
Notes being made upon surrender of such Series   Notes to the Paying Agent.
Payments of interest (including interest on any Interest Payment Date) will be
made, subject to such surrender where applicable, at the option of the
Corporation, (i) by check mailed to the address of the Person entitled thereto
as such address shall appear in the Security Register or (ii) by wire transfer
at such place and to such account at a banking institution in the United States
as may be designated in writing to the Trustee at least sixteen (16) days prior
to the date for payment by the Person entitled thereto.

The Corporation shall pay, as additional interest on the Series   Notes, when
due to the United States or any other taxing authority, the amounts set forth
in clause (i) of the definition of Additional Interest.

Section 104. Deferral of Interest Payments. The Corporation has the right at
any time and from time to time to extend (by prior agreement or otherwise) the
interest payment period of the Series   Notes for up to    ( ) consecutive
quarters (each, an "Extension Period"), during which Extension Period the
Corporation shall have the right to make partial payments of interest on any
Interest Payment Date; provided, however, that no such Extension Period may
extend beyond the Stated Maturity. Notwithstanding the foregoing, the
Corporation has no right to extend its obligation to pay such amounts as are
defined in clause (i) of the definition of Additional Interest. Prior to the
termination of any such Extension Period, the Corporation may further extend
(by prior agreement or otherwise) the interest payment period; provided that
such Extension Period, together with all such previous and further extensions
of that Extension Period, shall not exceed    ( ) consecutive quarters. Upon
the termination of any such Extension Period and upon the payment of all
accrued and unpaid interest and any Additional Interest then due, the
Corporation may select a new Extension Period, subject to the above limitations
and requirements.

Upon the termination of any Extension Period, which termination shall be on an
Interest Payment Date, the Corporation shall pay all Deferred Interest on the
next succeeding Interest Payment Date to the Person or Persons in whose name
the Series   Notes are registered on the Regular Record Date for such Interest
Payment Date; provided that Deferred Interest payable at Stated Maturity or on
any Redemption Date will be paid to the Person or Persons to whom principal is
payable.


                                       5
<PAGE>

The Corporation shall give the Holder or Holders of the Series   Notes and the
Trustee notice, as provided in Sections 105 and 106, respectively, of the
Original Indenture, of the occurrence, its selection or extension of an
Extension Period at least one Business Day prior to the earlier of (i) the
Regular Record Date relating to the Interest Payment Date on which the
Extension Period is to commence or relating to the Interest Payment Date on
which an Extension Period that is being extended would otherwise terminate, or
(ii) the date the Corporation or the Securities Trust is required to give
notice to the New York Stock Exchange or other applicable self-regulatory
organization of the record date or the date such distributions are payable. The
Corporation shall cause the Securities Trust to give notice of the occurrence
or the Corporation's selection of such Extension Period to Holders of the Trust
Securities. The month in which any notice is given pursuant to the immediately
preceding sentence of this Section shall constitute the first month of the
first quarter of the      (  ) consecutive quarters which comprise the maximum
Extension Period.

At any time any of the foregoing notices are given to the Trustee, the
Corporation shall give to the Paying Agent for the Series   Notes such
information as said Paying Agent shall reasonably require in order to fulfill
its tax reporting obligations with respect to such Series   Notes.

Section 105. Denominations. The Series   Notes may be issued in denominations
of $   or any integral multiple thereof.

Section 106. Global Securities. If the Series   Notes are distributed to
holders of the Trust Securities in liquidation of such holders' interests
therein, the Series   Notes will be issued in the form of one or more Global
Securities registered in the name of the Depositary (which shall be The
Depository Trust Company) or its nominee. Except under the limited
circumstances described below, Series   Notes represented by such Global
Security or Global Securities will not be exchangeable for, and will not
otherwise be issuable as, Series   Notes in definitive form. The Global
Securities described above may not be transferred except by the Depositary to a
nominee of the Depositary or by a nominee of the Depositary to the Depositary
or another nominee of the Depositary or to a successor Depositary or its
nominee.

Owners of beneficial interests in such a Global Security will not be considered
the Holders thereof for any purpose under the Indenture, and no Global Security
representing a Series   Note shall be exchangeable, except for another Global
Security of like denomination and tenor to be registered in the name of the
Depositary or its nominee or to a successor Depositary or its nominee or except
as described below. The rights of Holders of such Global Security shall be
exercised only through the Depositary.

A Global Security shall be exchangeable for Series   Notes registered in the
names of persons other than the Depositary or its nominee only if (i) the
Depositary notifies the Corporation that it is unwilling or unable to continue
as a Depositary for such Global Security and no successor Depositary shall have
been appointed by the Corporation within 90 days of receipt by the Corporation
of such notification, or if at any time the Depositary ceases to be a clearing
agency registered under the Exchange Act at a time when the Depositary is
required to be so registered to act as such Depositary and no successor
Depositary shall have been appointed by the Corporation within 90 days after it
becomes aware of such cessation, or (ii) the Corporation in its sole discretion
determines that such Global Security shall be so exchangeable. Any Global
Security that is

                                       6
<PAGE>

exchangeable pursuant to the preceding sentence shall be exchangeable for
Series   Notes registered in such names as the Depositary shall direct.

Section 107. Redemption. The Series   Notes shall be subject to redemption at
the option of the Corporation, in whole or in part, without premium or penalty,
at any time or from time to time on or after          ,     , at a Redemption
Price equal to 100% of the principal amount to be redeemed plus accrued but
unpaid interest (including any Additional Interest) to the Redemption Date;
provided, however, that, if a redemption in part shall result in the delisting
of the Preferred Securities, the Corporation may redeem the Series   Notes only
in whole. In addition, upon the occurrence of a Special Event, the Corporation
may, within ninety (90) days following the occurrence thereof and subject to
the terms and conditions of the Indenture, redeem the Series   Notes, in whole,
at a price equal to 100% of the principal amount to be redeemed plus any
accrued but unpaid interest (including Additional Interest, if any) to the
Redemption Date.

In the event of redemption of the Series   Notes in part only, a new Series
Note or Notes for the unredeemed portion shall be issued in the name or names
of the Holders thereof upon the surrender thereof.

The Series   Notes shall not have a sinking fund.

Notice of redemption shall be given as provided in Section 1104 of the Original
Indenture. Notwithstanding the foregoing, no notice of redemption that is given
pursuant to such Section with respect to any Series   Notes shall, while any
Preferred Securities are outstanding, contain a condition that provides that
redemption of the Series   Notes, or the part thereof, specified therein, shall
be conditional upon receipt by the Trustee or the Paying Agent for such Series
  Notes, on or prior to the date fixed for such redemption, of money sufficient
to pay the principal of and any interest on such Series   Notes. Any notice
provided to the Trustee under Section 1102 of the Original Indenture shall also
be provided by the Corporation to the Property Trustee; provided that the
Corporation shall provide notice pursuant to such Section 1102 on a date less
than 45 days prior to the Redemption Date only if such shorter notice is
satisfactory to both the Trustee and the Property Trustee.

Any redemption of less than all of the Series   Notes shall, with respect to
the principal thereof, be divisible by $  .

Section 108. Additional Interest. Whenever there is mentioned in the Indenture,
in any context, the payment of the principal of, or any premium or interest on,
or in respect of, Securities of any series, such mention shall, with respect to
the Series   Notes, be deemed to include mention of the payment of Additional
Interest provided for by the terms of the Series   Notes to the extent that, in
such context, Additional Interest is, was or would be payable in respect
thereof pursuant to such terms, and express mention of the payment of
Additional Interest in any provisions of this     Supplemental Indenture shall
not be construed as excluding Additional Interest in those provisions of the
Original Indenture or this     Supplemental Indenture in which such express
mention is not made.

If, subsequent to the date that a satisfaction and discharge or Defeasance is
effected pursuant to Section 401 or 1302, respectively, of the Original
Indenture, Additional Interest (for purposes of this

                                       7
<PAGE>

paragraph, as defined in clause (i) of the definition thereof) (in excess of
that established as of the date that such discharge or Defeasance is effected)
becomes payable in respect of the Series   Notes so discharged or defeased, the
Corporation shall irrevocably deposit or cause to be irrevocably deposited in
accordance with the provisions of Section 401 or 1304 of the Original
Indenture, as the case may be, within ten Business Days prior to the date the
first payment in respect of any portion of such excess Additional Interest
becomes due, such additional moneys or Government Obligations as are necessary
to satisfy the provisions of Section 401 or 1304 of the Original Indenture, as
the case may be, as if a discharge or Defeasance were being effected as of the
date of such subsequent deposit.

Except as otherwise provided in or pursuant to the Indenture, at least 10 days
prior to the first Interest Payment Date upon which Additional Interest (for
purposes of this paragraph, as defined in clause (i) of the definition thereof)
shall be payable, and at least 10 days prior to each date of payment of
principal and any premium or interest if there has been any change with respect
to the information set forth in the Officers' Certificate hereinafter
mentioned, the Corporation shall furnish the Trustee and any Paying Agent, if
other than the Trustee or the Corporation, with an Officers' Certificate
stating the amount of the Additional Interest payable per minimum authorized
denomination of the Series   Notes.

Section 109. Limitations on Dividend and Certain Other Payments. The
Corporation covenants, for the benefit of the Holders of the Series   Notes,
that, subject to the next succeeding sentence, (a) the Corporation shall not
declare or pay any dividend on, or make any distributions with respect to, or
redeem, purchase, acquire or make a liquidation payment with respect to, any of
its capital stock, and (b) the Corporation shall not make any payment of
interest, principal or premium, if any, on or repay, repurchase or redeem any
debt securities (including guarantees other than the Guarantee) issued by the
Corporation which rank pari passu with or junior to the Series   Notes (i) if
at such time the Corporation shall have given notice of its election to extend
an interest payment period for the Series   Notes and such extension shall be
continuing or (ii) if at such time an Event of Default with respect to the
Series   Notes shall have occurred and be continuing. The preceding sentence,
however, shall not restrict (A) any of the actions described in the preceding
sentence resulting from any reclassification of the Corporation's capital stock
or the exchange or conversion of one class or series of the Corporation's
capital stock for another class or series of the Corporation's capital stock or
(B) dividends or distributions in capital stock of the Corporation.

Section 110. Covenants Regarding Securities Trust. For so long as the Trust
Securities remain outstanding, the Corporation covenants (i) directly or
indirectly to maintain 100% ownership of the Common Securities (as defined in
the Trust Agreement) of the Securities Trust; provided, however, that any
permitted successor of the Corporation under the Indenture may succeed to the
Corporation's ownership of such Common Securities, and (ii) to use its
reasonable efforts to cause the Securities Trust (a) to remain a statutory
business trust, except in connection with the distribution of Series   Notes to
the holders of Trust Securities in liquidation of the Securities Trust, the
redemption of all of the Trust Securities, or certain mergers, consolidations
or amalgamations, each as permitted under the Trust Agreement, and (b) to
otherwise continue to be classified as a grantor trust for United States
federal income tax purposes. The Corporation shall deliver to the Trustee, no
later than the Business Day on which the event occurs, written notice of the
liquidation, dissolution

                                       8
<PAGE>

or winding-up of the Securities Trust if such liquidation, dissolution or
winding-up would occur earlier than the Stated Maturity of the Series   Notes
owned by such Securities Trust.

Section 111. No Fiduciary Duty of Trustee to Holders of Trust Securities. The
Trustee shall not be deemed to owe any fiduciary duty to the holders of Trust
Securities and shall be entitled to rely on the delivery to it of a written
notice by a Person representing himself to be a holder of a Trust Security to
establish that such Person is such a holder.

Section 112. Listing of Series   Notes. If the Series   Notes are to be issued
as a Global Security in connection with the distribution of the Series   Notes
to the holders of the Preferred Securities, the Corporation shall use its best
efforts to list such Series   Notes on the New York Stock Exchange or any other
exchange on which such Preferred Securities are then listed. The Corporation
shall notify the Trustee if and when the Series    Notes become admitted to
trading on the New York Stock Exchange or any other national securities
exchange.

Section 113. Covenant Defeasance. Section 1303 of the Original Indenture shall
not apply to any of the Series   Notes.

Section 114. Set-Off. Notwithstanding anything to the contrary in the Indenture
or in any Series   Note, prior to the dissolution of the Securities Trust, the
Corporation shall have the right to set off and apply against any payment it is
otherwise required to make hereunder or thereunder with respect to the
principal of or interest (including any Additional Interest) on the Series
Notes with and to the extent the Corporation has theretofore made, or is
concurrently on the date of such payment making, a payment with respect to the
Preferred Securities under the Guarantee. Contemporaneously with, or as
promptly as practicable after, any such payment under the Guarantee, the
Corporation shall deliver to the Trustee an Officers' Certificate (upon which
the Trustee shall be entitled to rely conclusively without any requirement to
investigate the facts contained therein) to the effect that such payment has
been made and that, as a result of such payment, the corresponding payment
under the Series   Notes has been set off in accordance with this Section 114.

Section 115. Subordination. The indebtedness evidenced by the Series   Notes
shall be, to the extent and in the manner set forth in the Original Indenture,
subordinate and junior in right of payment to the prior payment in full of all
Senior Indebtedness (as defined in the Original Indenture) with respect to the
Series   Notes, and the Series   Notes shall rank pari passu in right of
payment with each other series of Securities issued under the Indenture, with
the exception of any series of Securities which by its terms provides
otherwise.

Section 116. Paying Agent. The Trustee shall initially serve as Paying Agent
with respect to the Series   Notes, with the Place of Payment initially being
the Corporate Trust Office of the Trustee.

                                   ARTICLE 2

                            Miscellaneous Provisions

Section 201. Recitals by Corporation. The recitals in this     Supplemental
Indenture are made by the Corporation only and not by the Trustee, and all of
the provisions contained in the Original Indenture in respect of the rights,
privileges, immunities, powers and duties of the Trustee shall be applicable in
respect of the Series   Notes and of this     Supplemental Indenture as fully
and with like effect as if set forth herein in full.

                                       9
<PAGE>

Section 202. Ratification and Incorporation of Original Indenture. As
supplemented hereby, the Original Indenture is in all respects ratified and
confirmed, and the Original Indenture and this     Supplemental Indenture shall
be read, taken and construed as one and the same instrument.

Section 203. Executed in Counterparts. This     Supplemental Indenture may be
executed in several counterparts, each of which shall be deemed to be an
original, and such counterparts shall together constitute but one and the same
instrument.

Section 204. Assignment. The Corporation shall have the right at all times to
assign any of its rights or obligations under this Indenture with respect to
the Series   Notes to a direct or indirect wholly-owned subsidiary of the
Corporation; provided that, in the event of any such assignment, the
Corporation shall remain primarily liable for the performance of all such
obligations. The Indenture may also be assigned by the Corporation in
connection with a transaction described in Article Eight of the Original
Indenture.

Section 205. Enforcement by Holders of Preferred Securities of Right of Holders
to Receive Principal and Interest. So long as the Series   Notes are held by
the Property Trustee on behalf of the Securities Trust, a registered holder of
Preferred Securities may institute a legal proceeding directly against the
Corporation, without first instituting a legal proceeding directly against or
requesting or directing that action be taken by the Property Trustee or any
other Person, for enforcement of payment to such registered holder of principal
of or interest on Series   Notes having a principal amount equal to the
aggregate stated liquidation amount of such Preferred Securities of such
registered holder on or after the due dates therefor specified or provided for
in the Series   Notes. This Section 205 and Section 109 of this
Supplemental Indenture are for the benefit of the registered holders of
Preferred Securities and, prior to the dissolution of the Securities Trust, may
be enforced by such holders. A holder of a Preferred Security shall not have
the right, as such holder, to enforce any other provision of the Indenture.

IN WITNESS WHEREOF, each party hereto has caused this instrument to be signed
in its name and behalf by its duly authorized officers, all as of the day and
year first above written.

                                          Duke Capital Corporation

                                          By: _________________________________

Attest:
_________________________________

                                          The Chase Manhattan Bank,
                                            as Trustee

                                          By: _________________________________

Attest:
_________________________________

                                       10
<PAGE>

                                                                      EXHIBIT A

                                    FORM OF

                     SERIES    % JUNIOR SUBORDINATED NOTE

                              DUE

No.                                                         CUSIP No.

THE INDEBTEDNESS EVIDENCED BY THIS SECURITY IS, TO THE EXTENT PROVIDED IN THE
INDENTURE, SUBORDINATE AND SUBJECT IN RIGHT OF PAYMENT TO THE PRIOR PAYMENT IN
FULL OF ALL SENIOR INDEBTEDNESS, AND THIS SECURITY IS ISSUED SUBJECT TO THE
PROVISIONS OF THE INDENTURE WITH RESPECT THERETO.

                           DUKE CAPITAL CORPORATION

                     SERIES    % JUNIOR SUBORDINATED NOTE

                              DUE

<TABLE>
<S>                       <C>
Principal Amount:         $
Regular Record Date:      15th calendar day prior to Interest Payment Date
Original Issue Date:               ,
Stated Maturity:                   ,
Interest Payment Dates:   March 31, June 30, September 30, December 31
Interest Rate:             % per annum
Authorized Denomination:  $   or any integral multiple thereof
Initial Redemption Date:           ,
</TABLE>

Duke Capital Corporation, a Delaware corporation (the "Corporation," which
term includes any successor corporation under the Indenture referred to on the
reverse hereof), for value received, hereby promises to pay to
                      , or registered assigns, the principal sum of
DOLLARS ($      ) on the Stated Maturity shown above (or upon earlier
redemption), and to pay interest thereon from the Original Issue Date shown
above, or from the most recent Interest Payment Date to which interest has
been paid or duly provided for, quarterly in arrears on each Interest Payment
Date as specified above, commencing on          ,     , and on the Stated
Maturity (or upon earlier redemption) at the rate per annum shown above (the
"Interest Rate") until the principal hereof is paid or made available for
payment and on any overdue principal and on any overdue installment of
interest. The interest so payable, and punctually paid or duly provided for,
on any Interest Payment Date (other than an Interest Payment Date that is the
Stated Maturity or a Redemption Date) will, as provided in such Indenture, be
paid to the Person in whose name this Series    % Junior Subordinated Note due
         ,      (this "Security") is registered at the close of business on
the Regular Record Date as specified above next preceding such Interest
Payment Date; provided that any interest payable at Stated Maturity or on any
Redemption Date will be paid to the Person to whom principal

                                      A-1
<PAGE>

is payable. Except as otherwise provided in the Indenture, any such interest
not so punctually paid or duly provided for will forthwith cease to be payable
to the Holder on such Regular Record Date and may either be paid to the Person
in whose name this Security is registered at the close of business on a Special
Record Date for the payment of such Defaulted Interest to be fixed by the
Trustee, notice whereof shall be given to Holders of Securities of this series
not less than 10 days prior to such Special Record Date, or be paid at any time
in any other lawful manner not inconsistent with the requirements of any
securities exchange, if any, on which the Securities of this series shall be
listed, and upon such notice as may be required by any such exchange, all as
more fully provided in said Indenture.

Payments of interest on this Security will include interest accrued to but
excluding the respective Interest Payment Dates. Interest payments for this
Security shall be computed and paid on the basis of a 360-day year of twelve
30-day months. In the event that any date on which interest is payable on this
Security is not a Business Day, then payment of the interest payable on such
date will be made on the next succeeding day that is a Business Day (and
without any interest or payment in respect of any such delay), except that, if
such Business Day is in the next succeeding calendar year, payment shall be
made on the immediately preceding Business Day, in each case with the same
force and effect as if made on the date the payment was originally payable.
"Business Day" means a day other than (i) a Saturday or a Sunday, (ii) a day on
which banks in New York, New York are authorized or obligated by law or
executive order to remain closed or (iii) a day on which the Corporate Trust
Office or the principal corporate trust office of the Property Trustee is
closed for business.

The Corporation shall have the right at any time and from time to time during
the term of this Security to extend (by prior agreement or otherwise) the
interest payment period of such Security for up to    consecutive quarters
(each, an "Extension Period"), but not beyond the Stated Maturity of this
Security, during which Extension Periods interest shall accrue on unpaid
installments of interest at the Interest Rate, compounded quarterly, to the
date of payment to the extent permitted by applicable law (such unpaid interest
plus such interest thereon being called "Deferred Interest"); provided,
however, that the Corporation shall have the right to make partial payments of
interest on any Interest Payment Date during any Extension Period. Upon the
termination of each Extension Period, which shall be an Interest Payment Date,
the Corporation shall pay all Deferred Interest on the next succeeding Interest
Payment Date to the Person in whose name this Security is registered at the
close of business on the Regular Record Date for such Interest Payment Date;
provided that any Deferred Interest payable at Stated Maturity or on any
Redemption Date will be paid to the Person to whom principal is payable. Prior
to the termination of any such Extension Period, the Corporation may further
extend (by prior agreement or otherwise) the interest payment period; provided
that such Extension Period together with all such previous and further
extensions thereof shall not exceed    ( ) consecutive quarters. Upon the
termination of any such Extension Period, and the payment of all accrued and
unpaid interest (including any Additional Interest) then due, the Corporation
may agree to or select a new Extension Period, subject to the above
requirements. The Corporation shall not (i) declare or pay any dividend or
distribution on, or redeem, purchase, acquire or make a liquidation payment
with respect to, any of its capital stock, and (ii) make any payment of
interest, principal or premium, if any, on or repay, repurchase or redeem any
debt securities (including guarantees other than the Guarantee) issued by the
Corporation that rank pari passu with or junior to this Security if

                                      A-2
<PAGE>

the Corporation shall have given notice of its election to extend an interest
payment period for this Security and such extension shall be continuing or if
at such time an Event of Default with respect to the series of which this
Security is a part shall have occurred and be continuing. The preceding
sentence, however, shall not restrict (A) any of the actions described in the
preceding sentence resulting from any reclassification of the Corporation's
capital stock or the exchange or conversion of one class or series of the
Corporation's capital stock for another class or series of the Corporation's
capital stock or (B) dividends or distributions in capital stock of the
Corporation. The Corporation shall give the Holder of this Security and the
Trustee notice of the occurrence, its selection or extension of an Extension
Period at least one Business Day prior to the earlier of (i) the Regular Record
Date relating to the Interest Payment Date on which the Extension Period is to
commence or relating to the Interest Payment Date on which an Extension Period
that is being extended would otherwise terminate or (ii) the date the
Corporation or the Securities Trust is required to give notice to the New York
Stock Exchange or other applicable self-regulatory organization of the record
date or the date such distributions are payable.

The Corporation also shall be obligated to pay when due and without extension
all additional amounts as may be required so that the net amount received and
retained by the Holder of this Security (if the Holder is the Securities Trust)
after paying taxes, duties, assessments or governmental charges of whatever
nature (other than withholding taxes) imposed by the United States or any other
taxing authority will not be less than the amounts such Holder would have
received had no such taxes, duties, assessments, or other governmental charges
been imposed.

Payment of the principal of and interest (including Additional Interest, if
any) due at the Stated Maturity or earlier redemption of this Security shall be
made upon surrender of this Security, at the Corporate Trust Office of the
Trustee, in such coin or currency of the United States of America as at the
time of payment is legal tender for payment of public and private debts.
Payment of interest (including interest on an Interest Payment Date) will be
made, subject to such surrender where applicable, at the option of the
Corporation, (i) by check mailed to the address of the Person entitled thereto
as such address shall appear in the Security Register or (ii) by wire transfer
at such place and to such account at a banking institution in the United States
as may be designated in writing to the Trustee at least sixteen (16) days prior
to the date for payment by the Person entitled thereto.

The indebtedness evidenced by this Security is, to the extent and in the manner
set forth in the Indenture, subordinate in right of payment to the prior
payment in full of all Senior Indebtedness (as defined in the Indenture), and
this Security is issued subject to the provisions of the Indenture with respect
thereto. Each Holder of this Security, by accepting the same, (a) agrees to and
shall be bound by such provisions, (b) authorizes and directs the Trustee on
his behalf to take such action as may be necessary or appropriate to effectuate
the subordination so provided and (c) appoints the Trustee his attorney-in-fact
for any and all such purposes. Each Holder hereof, by his acceptance hereof,
waives all notice of the acceptance of the subordination provisions contained
herein and in the Indenture by each holder of Senior Indebtedness whether now
outstanding or hereafter incurred and waives reliance by each such holder upon
said provisions.

REFERENCE IS HEREBY MADE TO THE FURTHER PROVISIONS OF THIS SECURITY SET FORTH
ON THE REVERSE HEREOF, WHICH FURTHER PROVISIONS SHALL FOR ALL PURPOSES HAVE THE
SAME EFFECT AS IF SET FORTH AT THIS PLACE.

                                      A-3
<PAGE>

Unless the certificate of authentication hereon has been executed by the
Trustee by manual signature, this Security shall not be entitled to any benefit
under the Indenture or be valid or obligatory for any purpose.

IN WITNESS WHEREOF, the Corporation has caused this instrument to be duly
executed under its corporate seal.

Dated:

                                          Duke Capital Corporation

                                          By: _________________________________

Attest:
_________________________________

                                      A-4
<PAGE>

                         CERTIFICATE OF AUTHENTICATION

This is one of the Securities of the series designated therein referred to in
the within-mentioned Indenture.

                                          The Chase Manhattan Bank,
                                           as Trustee

                                          By: _________________________________
                                                   Authorized Officer

                                      A-5
<PAGE>

                           (Reverse Side of Security)

This Security is one of a duly authorized issue of Securities of the
Corporation (the "Securities"), issued and issuable in one or more series under
a Subordinated Indenture, dated as of April 1, 1998, as supplemented (the
"Indenture"), between the Corporation and The Chase Manhattan Bank, as Trustee
(the "Trustee," which term includes any successor trustee under the Indenture),
to which Indenture and all indentures supplemental thereto reference is hereby
made for a statement of the respective rights, limitation of rights, duties and
immunities thereunder of the Corporation, the Trustee and the Holders of the
Securities issued thereunder and of the terms upon which said Securities are,
and are to be, authenticated and delivered. This Security is one of the series
designated on the face hereof as Series    % Junior Subordinated Notes due
         ,      (the "Series   Notes") in the aggregate principal amount of up
to $         . Capitalized terms used herein for which no definition is
provided herein shall have the meanings set forth in the Indenture.

The Corporation shall have the right, subject to the terms and conditions of
the Indenture, to redeem this Security at any time on or after          ,
at the option of the Corporation, without premium or penalty, in whole or in
part, at a Redemption Price equal to 100% of the principal amount to be
redeemed plus accrued but unpaid interest (including any Additional Interest)
to the Redemption Date. Upon the occurrence of a Special Event (as defined
below), the Corporation may, within 90 days following the occurrence thereof
and subject to the terms and conditions of the Indenture, redeem this Security
without premium or penalty, in whole, at a Redemption Price equal to 100% of
the principal amount thereof plus accrued but unpaid interest (including any
Additional Interest) to the Redemption Date. A Special Event may be a Tax Event
or an Investment Company Act Event. "Tax Event" means that the Administrative
Trustees and the Corporation shall have received an Opinion of Counsel
experienced in such matters to the effect that, as a result of (a) any
amendment to, or change (including any announced prospective change) in, laws
(or any regulations thereunder) of the United States or any political
subdivision or taxing authority thereof or therein or (b) any amendment to, or
change in, an interpretation or application of such laws or regulations, there
is more than an insubstantial risk that (i) the Securities Trust would be
subject to United States federal income tax with respect to income accrued or
received on the Series   Notes, (ii) interest payable on the Series   Notes
would not be deductible by the Corporation for United States federal income tax
purposes, or (iii) the Securities Trust would be subject to more than a de
minimis amount of other taxes, duties or other governmental charges, which
change or amendment becomes effective on or after the Original Issue Date.
"Investment Company Act Event" means that the Administrative Trustees and the
Corporation shall have received an Opinion of Counsel experienced in such
matters to the effect that, as a result of the occurrence of a change in law or
regulation or a written change in interpretation or application of law or
regulation by any legislative body, court, governmental agency or regulatory
authority, there is more than an insubstantial risk that the Securities Trust
is or will be considered an "investment company" that is required to be
registered under the Investment Company Act of 1940, as amended, which change
becomes effective on or after the Original Issue Date.

In the event of redemption of this Security in part only, a new Security or
Securities of this series for the unredeemed portion hereof will be issued in
the name of the Holder hereof upon the surrender hereof. The Securities of this
series will not have a sinking fund.

                                      A-6
<PAGE>

If an Event of Default with respect to the Securities of this series shall
occur and be continuing, the principal of the Securities of this series may be
declared due and payable in the manner, with the effect and subject to the
conditions provided in the Indenture.

The Indenture permits, with certain exceptions as therein provided, the
amendment thereof and the modification of the rights and obligations of the
Corporation and the rights of the Holders of the Securities of all series
affected under the Indenture at any time by the Corporation and the Trustee
with the consent of the Holders of not less than a majority in principal amount
of the Outstanding Securities of all series affected thereby (voting as one
class). The Indenture contains provisions permitting the Holders of not less
than a majority in principal amount of the Outstanding Securities of all series
with respect to which a default under the Indenture shall have occurred and be
continuing (voting as one class), on behalf of the Holders of the Securities of
all such series, to waive, with certain exceptions, such default under the
Indenture and its consequences. The Indenture also permits the Holders of not
less than a majority in principal amount of the Securities of each series at
the time Outstanding, on behalf of the Holders of all Securities of such
series, to waive compliance by the Corporation with certain provisions of the
Indenture affecting such series. Any such consent or waiver by the Holder of
this Security shall be conclusive and binding upon such Holder and upon all
future Holders of this Security and of any Security issued upon the
registration of transfer hereof or in exchange hereof or in lieu hereof,
whether or not notation of such consent or waiver is made upon this Security.

No reference herein to the Indenture and no provision of this Security or of
the Indenture shall alter or impair the obligation of the Corporation, which is
absolute and unconditional, to pay the principal of and interest on this
Security at the times, place and rate, and in the coin or currency, herein
prescribed.

As provided in the Indenture and subject to certain limitations therein set
forth, the transfer of this Security is registrable in the Security Register,
upon surrender of this Security for registration of transfer at the office or
agency of the Corporation for such purpose, duly endorsed by, or accompanied by
a written instrument of transfer in form satisfactory to the Corporation and
the Security Registrar and duly executed by, the Holder hereof or his attorney
duly authorized in writing, and thereupon one or more new Securities of this
series, of authorized denominations and of like tenor and for the same
aggregate principal amount, will be issued to the designated transferee or
transferees. No service charge shall be made for any such registration of
transfer or exchange, but the Corporation may require payment of a sum
sufficient to cover any tax or other governmental charge payable in connection
therewith.

As provided in and subject to the provisions of the Indenture, the Holder of
this Security shall not have the right to institute any proceeding with respect
to the Indenture or for the appointment of a receiver or trustee or for any
other remedy thereunder, unless such Holder shall have previously given the
Trustee written notice of a continuing Event of Default with respect to the
Securities of this series, the Holders of not less than a majority in principal
amount of the Securities of this series at the time Outstanding shall have made
written request to the Trustee to institute proceedings in respect of such
Event of Default as Trustee and offered the Trustee reasonable indemnity, and
the Trustee shall not have received from the Holders of a majority in principal
amount of Securities of this series at the time Outstanding a direction
inconsistent with such request and shall have failed to

                                      A-7
<PAGE>

institute any such proceeding for 60 days after receipt of such notice, request
and offer of indemnity. The foregoing shall not apply to any suit instituted by
the Holder of this Security for the enforcement of any payment of principal
hereof or any interest hereon on or after the respective due dates expressed
herein.

The Indenture contains provisions for defeasance at any time of the entire
indebtedness of the Securities of this series upon compliance with certain
conditions set forth in the Indenture.

Prior to due presentment of this Security for registration of transfer, the
Corporation, the Trustee and any agent of the Corporation or the Trustee may
treat the Person in whose name this Security is registered as the owner hereof
for all purposes, whether or not this Security be overdue, and neither the
Corporation, the Trustee nor any such agent shall be affected by notice to the
contrary.

The Securities of this series are issuable only in registered form without
coupons in denominations of $   and any integral multiple thereof. As provided
in the Indenture and subject to the limitations therein set forth, Securities
of this series are exchangeable for a like aggregate principal amount of
Securities of this series of a different authorized denomination, as requested
by the Holder surrendering the same upon surrender of the Security or
Securities to be exchanged at the office or agency of the Corporation.

This Security shall be governed by, and construed in accordance with, the
internal laws of the State of New York.

                                      A-8
<PAGE>

                                 ABBREVIATIONS

The following abbreviations, when used in the inscription on the face of this
instrument, shall be construed as though they were written out in full
according to applicable laws or regulations:

TEN COM -- as tenants in common      UNIF GIFT MIN ACT --      Custodian
                                                         ------          -------
TEN ENT -- as tenants by the entireties                  (Cust)          (Minor)


JT TEN -- as joint tenants with                        under Uniform Gifts to
         rights of survivorship and                    Minors Act _____________
         not as tenants in common                                   (State)


    Additional abbreviations may also be used though not on the above list.

FOR VALUE RECEIVED, the undersigned hereby sell(s) and transfer(s) unto
      (please insert Social Security or other identifying number of assignee)

--------------------------------------------------------------------------------
    Please Print or Typewrite Name and Address, Including Postal Zip Code of
                                    Assignee


--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
the within Security and all rights thereunder, hereby irrevocably constituting
and appointing


--------------------------------------------------------------------------------

--------------------------------------------------------------------------------
agent to transfer said Security on the books of the Corporation, with full
power of substitution in the premises.

Dated: ______________________________     -------------------------------------

                                          -------------------------------------
                                          NOTICE: The signature to this
                                          assignment must correspond with the
                                          name as written upon the face of the
                                          within instrument in every
                                          particular without alteration or
                                          enlargement, or any change whatever.

                                      A-9
<PAGE>

                                                                       EXHIBIT B

                         CERTIFICATE OF AUTHENTICATION

  This is one of the Securities of the series designated therein referred to in
the within-mentioned Indenture.

                                          The Chase Manhattan Bank,
                                           as Trustee

                                          By: _________________________________
                                                    Authorized Officer

                                      B-1